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c390be6a5d
This change attempts to simplify (X^Y) -> X or Y in the user's context if we know that
only bits from X or Y are demanded.
A minimized case is provided bellow. This change will simplify "t>>16" into "var1 >>16".
=============================================================
unsigned foo (unsigned val1, unsigned val2) {
unsigned t = val1 ^ 1234;
return (t >> 16) | t; // NOTE: t is used more than once.
}
=============================================================
Note that if the "t" were used only once, the expression would be finally optimized as well.
However, with with this change, the optimization will take place earlier.
Reviewed by Nadav, Thanks a lot!
llvm-svn: 169317
47 lines
1.1 KiB
LLVM
47 lines
1.1 KiB
LLVM
; RUN: opt -instcombine -S < %s | FileCheck %s
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; <rdar://problem/8606771>
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; CHECK: @main
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define i32 @main(i32 %argc) nounwind ssp {
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entry:
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%tmp3151 = trunc i32 %argc to i8
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; CHECK: %0 = shl i8 %tmp3151, 5
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; CHECK: and i8 %0, 64
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; CHECK-NOT: shl
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; CHECK-NOT: shr
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%tmp3161 = or i8 %tmp3151, -17
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%tmp3162 = and i8 %tmp3151, 122
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%tmp3163 = xor i8 %tmp3162, -17
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%tmp4114 = shl i8 %tmp3163, 6
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%tmp4115 = xor i8 %tmp4114, %tmp3163
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%tmp4120 = xor i8 %tmp3161, %tmp4115
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%tmp4126 = lshr i8 %tmp4120, 7
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%tmp4127 = mul i8 %tmp4126, 64
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%tmp4086 = zext i8 %tmp4127 to i32
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; CHECK: ret i32
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ret i32 %tmp4086
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}
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; rdar://8739316
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; CHECK: @foo
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define i8 @foo(i8 %arg, i8 %arg1) nounwind {
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bb:
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%tmp = shl i8 %arg, 7
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%tmp2 = and i8 %arg1, 84
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%tmp3 = and i8 %arg1, -118
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%tmp4 = and i8 %arg1, 33
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%tmp5 = sub i8 -88, %tmp2
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%tmp6 = and i8 %tmp5, 84
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%tmp7 = or i8 %tmp4, %tmp6
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%tmp8 = xor i8 %tmp, %tmp3
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%tmp9 = or i8 %tmp7, %tmp8
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%tmp10 = lshr i8 %tmp8, 7
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%tmp11 = shl i8 %tmp10, 5
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; CHECK: %tmp10 = lshr i8 %tmp8, 7
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; CHECK: %tmp11 = shl nuw nsw i8 %tmp10, 5
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%tmp12 = xor i8 %tmp11, %tmp9
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ret i8 %tmp12
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}
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